1. Field of the Invention
The present invention relates to an apparatus for controlling stiffness of an anti-roll bar for a vehicle, and more particularly, to an apparatus wherein piezoelectric ceramics are added to an anti-roll bar to allow the anti-roll bar to be controlled to exhibit its optimum stiffness according to vehicle conditions including vehicle speed and steering angle such that the driving stability and product value of vehicle can be maximized.
2. Description of the Background Art
In general, an anti-roll bar for a vehicle is a major element of the vehicle suspension system and is called a stabilizer. The anti-roll bar is configured to allow a central portion of a steel rod bent into a general ‘C’ shape to function as a torsion bar, and serves to cause no additional action when right and left wheels are simultaneously moved in a vertical direction and to increase its torsional stiffness due to its twisting operation when there is a difference between the vertical strokes of the right and left wheels.
In particular, when a vehicle body is subjected to rolling, the anti-roll bar functions as an auxiliary spring for causing spring action in response to the difference between the vertical strokes of the right and left wheels and is used to control steering characteristics since it can reduce the rolling and change the rolling stiffness of the right and left wheels.
That is, an anti-roll bar functions in such a manner that the degree of understeer is increased if the stiffness of a front anti-roll bar is increased while the degree of understeer is decreased if the stiffness of a rear anti-roll bar is increased.
FIG. 1 is a front view of a related art vehicle suspension system.
As shown in FIG. 1, a related art vehicle suspension system 20 absorbs vibration or shock transmitted to a vehicle body through tires at both sides thereof. In particular, lower arms 21, which are elements of the suspension system 20, are connected to the tires, respectively, and the both lower arms 21 are interconnected with each other through an anti-roll bar 10.
Therefore, the anti-roll bar 10 can reduce the rolling occurring when the vehicle travels along a curved road.
However, since the related art anti-roll bar for a vehicle is designed and used to exhibit constant stiffness, the stiffness of the anti-roll bar cannot be changed in accordance with rapidly changing vehicle driving conditions such as vehicle speed and steering angle. Thus, there is a problem in that the driving comfort or stability can be deteriorated due to the anti-roll bar with constant stiffness.